Goats are widely renowned for their courage. They are able to scale high cliffs and eat poison ivy without batting an eye. Is there no limit to their bravery? To find out, a group of scientists had the Dutch Air Force fly combat helicopters above some goats and measured if they got scared. Lu and Tirth discuss this perilous study on S01E07 of the Recreational Science podcast (timecode 30:55):
Tirth: The title of this study is, “Physiological and behavioral reactions elicited by simulated and real life visual and acoustic helicopter stimuli in dairy goats”. This was published in the journal BMC Veterinary Research.
Lu: Oh, good journal.
Tirth: Great journal. And all the authors are from the Netherlands. Great country.
Lu: Ah, yes, good country… I didn’t even know they had goats in the Netherlands.
Tirth: They have goats in the Netherlands. They also have helicopters. The study was at least partially, maybe fully funded by the Netherlands Air Force.
Lu: Because they provided the helicopters.
Tirth: Yes, yes. The premise of this study is that there’s a concern among goat farmers that loud noises from helicopters flying overhead can startle goats. This study tried to verify and quantify this. The researchers wanted to see if goats are being harmed, which may mean that helicopters should alter their routes.
Lu: So the helicopters flying by might affect like milk production from the goats.
Tirth: Yeah, or just like goat mating or whatever, you know.
Lu: I see.
Tirth: The first experiment is simulated. It was all done indoors. The researchers brought five goats into a barn with a giant screen. On this screen they flashed images of helicopters and played sounds of helicopters, three minutes at a time, multiple times a day, over five days.
Lu: Oh my god.
Tirth: They kept track of the goats’ heart rate and cortisol levels, as measures of stress, throughout the five days.
Lu: Very good.
Tirth: The next experiment is the real deal. They moved the goats outdoors and did two helicopter fly-bys.
Lu: Same goats?
Tirth: Yeah, same goats.
Lu: How close to the goats were the helicopters?
Tirth: 50 meters.
Lu: That’s pretty close.
Tirth: That’s a very low fly-by. And if it matters, because I like helicopters, the videos they played were of the Apache helicopters, and the fly-overs were done by Chinooks.
Lu: Good. Very intimidating helicopters.
Tirth: I will also note that the peak noise level for the helicopter simulation was 90 decibels, about the loudness of a hair dryer up close, which is pretty loud. The actual fly-by was like 100 decibels, so about twice as loud. So what do you think they found? And before you say anything, I think the real answer may surprise you.
Lu: Well, okay. So one of my concerns is that in the first experiment, in both experiments actually, what they should have done is strap the goats to a chair, strap them down by the arms and the legs…
Tirth: A Clockwork Orange.
Lu: …hold their eyes open with pins and make them stare at the screen.
Tirth: Diabolical but effective.
Lu: Since they didn’t do that, the goats could have just closed their eyes, could have just went to sleep or whatever. So maybe they didn’t have that big of a change in heart rate and cortisol levels due to helicopter noises.
Tirth: That’s exactly right. They did not find a change in heart rate and cortisol levels in response to the helicopters. Indoors or outdoors.
Lu: Oh, no change even with real air force helicopters flying by? The goats don’t care…
Tirth: But I’ll say this, behaviorally, they saw some changes, which they weren’t able to quantify. They did notice…
Lu: That the goats looked up?
Tirth: Yeah, the goats looked up. Both indoors and outdoors.
Lu: They looked up. Well, that at least assures you that these were not deaf and blind goats. That’s an important control.
Tirth: Yes then they also noted that some of the goats ran. Three out of five goats, I think, ran. One of them tried to escape and got injured.
Lu: Wait, they ran, but their heart rate didn’t go up?
Tirth: No, I think it’s just the sample size of five goats is too low and the variability is too high, you know?
Lu: Well, what they needed is a positive control, I think. Something they know will get the goats’ heart rate and cortisol levels to go up.
Tirth: What could have been a good positive control?
Lu: They could have shaved goats. That’ll probably get their hearts going.
Tirth: Or they could have set loose a mechanical tiger.
Lu: Yes, exactly. For future studies.
Article citation
van der Staay et al., 2011. Physiological and behavioral reactions elicited by simulated and real-life visual and acoustic helicopter stimuli in dairy goats. BMC Veterinary Research. https://bmcvetres.biomedcentral.com/articles/10.1186/1746-6148-7-16
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